The present invention relates to an actuator that actuates based upon an applied signal. In particular, it relates to determining the characteristics of the actuator to more precisely control the duration and magnitude of the actuation signal.
Actuators are devices that move in response to an applied signal. An example of an actuator is a microelectromechanical (MEM) device, which may be used in auto-focus cameras. MEM actuators also possess a characteristic capacitance that changes based on the actuators displacement. The response (e.g., ‘the displacement’) of the actuator to the applied voltage may be non-linear. Transfer functions may be derived that may be used in the linearization of the response of the actuator. In deriving the transfer function of an actuator, common end points related to, for example, the voltage related to the maximum displacement and an offset voltage related to the minimum displacement are frequently predetermined for the type of actuator to be used, and are pre-programmed into a microprocessor that controls the system. A microprocessor using the pre-programmed voltages and inputs from sensors can derive a response curve for the attached actuator. The preprogrammed offset voltage value and maximum displacement voltage value form a response curve. These values may be stored in a look up table.
The type of actuator with which the control and driving circuit is going to be used is commonly known ahead of time. However, the response curve of the actuator varies based on the type of actuator, as well as time, temperature and orientation of the actuator (e.g., when the device is held horizontally versus being held vertically). Therefore, complex calibration and temperature sensors are typically needed to provide an accurate linearization of the actuator response. Due to the need for a microprocessor, the complexity of the measurement system needed to provide the linear characterization of an actuator is prohibitive.
There is a need for an integrated circuit chip that is capable of determining the maximum displacement and offset voltages as well as other relevant information usable to characterize an actuator without the need for providing pre-programmed values or a microprocessor or regard for determining a time, an environmental temperature or device orientation.